The present invention relates to a variable valve timing system, and more particularly, to a line control arrangement for a continuously variable valve timing system.
One way in which engine performance can be improved is by opening and closing engine valves differently at low speeds and high speeds. In particular, varying the timing of the intake valves plays a significant role in air induction capability. Accordingly, by opening the intake valves early, a valve overlap interval is increased such that the inertial flow of intake and exhaust processes can be sufficiently utilized at high speeds to result in an increase in volumetric efficiency. However, at low speeds, this results in a decrease in volumetric efficiency and an increase in the exhaust of hydrocarbons from excess, unburned fuel.
To solve this problem, various configurations and methods have been developed that vary the timing of opening and closing of the intake and exhaust valves. One of the most recent developments is the continuously variable valve timing (CVVT) system. A significant drawback of such CVVT systems is that they generate undesirable impact sounds each time the valve timing system is adjusted. Accordingly, a CCVT system that reduces operating noise would be highly desirable.
The present invention provides a line control arrangements for continuously variable valve timing systems that reduce impact noise generated by operation of an oil controlling driver. In a preferred embodiment, the present invention comprises a valve timing controller generating a predetermined valve timing variable control signal according to an engine speed of a vehicle; and an oil controlling driver generating a rotational force in a predetermined direction according to the valve timing variable control signal received from the valve timing controller to form a corresponding advance line and a corresponding retard line.
According to an embodiment of the invention there is provided a line control arrangement for a continuously variable valve timing system of a vehicle. The line control arrangement includes a housing, and oil supply, a motor, an advance passageway, and a retard passageway. The oil supply shaft is rotatably mounted within the housing. The motor is configured to rotate the oil supply shaft to an advance position or a retard position based on a predetermined valve timing variable control signal received from a valve timing controller. The advance passageway is formed through the housing when the oil supply shaft is in the advance position, the advance passageway fluidly coupling an oil supply hole to an advance hole. The retard passageway is formed through the housing when the oil supply shaft is in the retard position, the retard passageway fluidly coupling an oil supply hole and a retard hole. The supply hole is configured to be fluidly coupled to an oil supply; the retard hole is configured to be coupled to a retard chamber in a vane housing; and the advance hole is configured to be coupled to an advance chamber in a vane housing. An advance drain channel is formed when the oil supply shaft is in the retard position, the advanced drain channel fluidly coupling the retard hole to an exhaust hole. A retard drain channel formed when the oil supply shaft is in the advance position, the retard drain channel fluidly coupling the advance hole to an exhaust hole. The advance passageway comprises a passageway defined by an advance body section coupled to the oil supply shaft, and the housing. The retard passageway comprises a passageway defined by a retard body section coupled to the oil supply shaft, and the housing.
Further according to the invention there is provided a method for controlling a continuously variable valve timing system of a vehicle. When a high engine speed is measured, a predetermined valve timing control signal generated. This signal is then transmitted to a motor coupled to an oil supply shaft. The motor rotates the oil supply shaft to an advance position to form an advance passageway coupling an oil supply hole to an advance hole. This allows fluid to flow through the advance passageway into an advance chamber of a vane housing, thereby moving a vane within the vane housing to alter valve timing. Later, when a lower speed is measured, another valve timing control signal is generated and transmitted to a motor coupled to the oil supply shaft. The oil supply shaft is then rotated to a retard position to form a retard passageway coupling an oil supply hole to a retard hole. This allows fluid to flow through the retard passageway into a retard chamber of the vane housing, thereby moving the vane within the vane housing to alter valve timing.